The field of network security has become increasingly important in today's society. In particular, the ability to effectively protect computers and systems presents a significant obstacle for component manufacturers, system designers, and network operators. This obstacle is made even more difficult due to the plethora of new security threats, which seem to evolve daily. Virtualization is a software technology allowing an operating system to run unmodified on an isolated virtual environment (typically referred to as a virtual machine), where a platform's physical characteristics and behaviors are reproduced. More specifically, a virtual machine can represent an isolated, virtual environment (lying on top of a host operating system (OS)) and equipped with virtual hardware (processor, memory, disks, network interfaces, etc.). Commonly, the virtual machine is managed by a virtualization product. A virtual machine monitor (VMM) is the virtualization software layer that manages hardware requests from a guest OS (e.g., simulating answers from real hardware). A hypervisor is computer software/hardware platform virtualization software that allows multiple operating systems to run on a host computer concurrently. Both Xen and Hypervisor represent forms of VMMs and these VMMs can be exploited to better protect computers and systems from emerging security threats.